1. Field of the Invention
The present invention relates to a method for producing an L-amino acid using a Vibrio bacterium, and more particularly, to a method for producing an L-amino acid such as L-lysine. L-lysine is industrially useful as an additive in animal feeds, and as a component of health foods, amino acid infusions, and the like.
2. Brief Description of the Related Art
L-amino acids such as L-lysine, L-glutamic acid, L-threonine, L-leucine, L-isoleucine, and L-valine are typically produced by fermentation using a coryneform bacterium belonging to the genus Brevibacterium or Corynebacterium, a bacterium belonging to the genus Bacillus, Escherichia, Streptomyces, Pseudomonas, Arthrobacter, Serratia, Enterobacter, Pantotea, Methylobacillus, or Vibrio, or a filamentous bacterium belonging to the genus Penicillium. 
There are well-known methods for producing a target substance such as an L-amino acid by fermentation using a microorganism, such as by using a wild-type microorganism (wild-type strain), using an auxotrophic strain derived from a wild-type strain, using a metabolic regulation mutant that is derived from a wild-type strain as a drug-resistant mutant, and using a strain having properties of both the auxotrophy and the metabolic regulation mutation.
The productivity of the L-amino acids has been significantly enhanced by improvements in chosen microorganism and production methods. However, to further meet increasing needs, producing L-amino acids at a low cost and high efficiency is required for the development of further methods.
It is a longstanding problem in the direct fermentation of L-amino acids is a decrease in the activity of the chosen microorganism caused by an increase in the osmotic pressure due to the accumulation of the product of interest during the culture, resulting in difficulty in keeping the productivity for a long period of time.
The Vibrio bacteria are Gram-negative facultative anaerobic bacteria belonging to the Vibrionanceae family in γ-Propionibacteria, and each of the bacteria moves by one polar flagellum. The Vibrio bacteria are present in fresh water and seawater.
For example, the following methods using cultures or bacterial cells of Vibrio bacteria, or treated products thereof are known: a method of producing L-tryptophan from indol and serine, or indol, pyruvic acid, and ammonium ion (JP 56-85291 A); a method of producing L-methionine from N-carbamylmethionine (JP 62-275696 A); a method of producing L-serine from β-hydroxyaspartic acid (JP 60-62993 A); a method of producing phenylalanine or a derivative thereof from a precursor of phenylalanine (JP 62-289194 A); and a method of producing thymidine by reacting 2-deoxyribose-1-phosphoric acid or a salt thereof with thymine (JP 1-104190 A).
A method of producing a target substance using a microorganism isolated from nature capable of producing the substance is also known. As such a method using a Vibrio bacterium, a bacterium which belongs to the genus Vibrio and can produce an eicosapentaenoic acid-containing lipid, and a method of producing eicosapentaenoic acid using the bacterium have been reported (JP 63-216490 A).
However, the ability of a Vibrio bacterium to produce a target substance such as an amino acid from sugar or the like by direct fermentation has not been previously reported, and an example of production of a target substance from sugar or the like by direct fermentation has not been reported. In addition, a Vibrio bacterium whose metabolism or the like has been modified to produce a target substance, and production of the substance using the bacterium are not known, and it has not been previously reported that the Vibrio bacterium is able to be employed to solve the above-mentioned problems.